Hello to everyone. I am new to this forum and also new to 3d printing. I had a look round and chose the Ord Bot as the best engineered DIY printer out there and I got a kit shipped to me in the UK from Automation Technology. The customs duty was a reasonable 35 GBP. I am nearly there with the build having spent about 40+ hours on it so far. Obviously a lot of thought and effort has gone into the design. I have an Arduino Mega 2560/Ramps 1.4 board/pololu stepper drivers. I also have the Smart LCD smart panel. Not sure which firmware was preloaded but I have now re flashed it with Marlin firmware and an Ord Bot configuration. Eventually got all the axis to move and extruder and bed to heat up. LCD smart controller worked OK both in stand alone mode and also powered through the USB from the PC. So far so good. One of the last things to complete was the end stops. Using just 2 of the 3 wires, I wired S on ramps to NO on the switch (blue wire) and GND to C (black wire). However disaster. I think I have plugged one of the endstops into the Ramps board upside down. Instead of S to GND this would connect + to GND. Something is damaged. The Ramps board will now not power up in stand alone mode. The screen lights up but there is no menu. As a test I tried an external 5v supply to the Arduino board power socket, the LEDS on the Arduino board light up but the RAMPS board LEDS and the screen are still dead. Strange thing is everything still works OK when RAMPS is powered from a PC through the USB connection with the mains power unit on at the same time. The screen and menu is back and axis movements control fine. I could run the printer like this but I would like to be able to use it in stand alone mode.Something on the 5v power side of the RAMPS board has been damaged I think. I checked the 2 resettable fuses with a meter and they both seem OK. Anybody got any ideas which components to check/replace or should I just cut my losses and buy a new board?

Looking at the schematic, it seems that the RAMPS board powers the Arduino with 12 V through its VIN pin, and lets the Arduino step it down to 5 V. So you must have fried the 5 V regulator on the Arduino. That also explains why it works with 5 V USB power -- the on-board regulator isn't used in that case.

It could be that D1 on the RAMPS is fried, or the diode on the Arduino board (immediately to the left of the header with IOREF, RESET, 3.3V etc).

The Arduino needs at least 7 V on its power connector, it definitely won't work with 5 V (although a LED or two may turn on). Powering the Arduino that way should also supply 5 V to RAMPS. If the regulator on the Arduino is broken, it will not work with external power, only with USB.

If it's the regulator, you can fix it by supplying 5 V yourself: use a LM7805 and a capacitor to get 5 V out of the 12 V supply. For a quick and dirty repair, you could simply solder the 7805 on top of the existing regulator (no capacitor needed in that case). I've circled the 5 V regulator on the Arduino in red.

If it's the D1 diode on the RAMPS, replace it, or simply short it then never connect anything to Arduino's power jack (put some tape on it). If it's the diode on the Arduino board, replace it -- don't short that one, it can hurt the computer's USB if you do.

D1 on the RAMPS board checks out OK (only by measuring forward and reverse resistance) and the board is giving +12v to the VIN pin which supplies the Arduino so I assume the RAMPS board is OK. The Arduino diode also checks out OK.

When I put an external 12v supply onto the VIN pin on the Arduino, the regulator does put out a 5v supply.

Connecting the Arduino and RAMPS boards together, the LEDs light up but the screen is still blank.

I also confirmed that if I supply an external 5v supply to the USB socket, the system works fine. So not sure what the problem is but I have ordered an LM7805.

I assume this is an LCD screen. Is there an adjustment for "contrast"? Check the viewing angle on it to see that it's just not skewed so far that you can't actually see it unless you're looking at an extreme angle.

Also, verify the pinouts and data setups for the data going to the display.

TLHarrell: Yes, I am talking about the stand alone LCD screen on my Ord Bot. The problem is not the contrast adjustment.

If I supply power via the USB connection - either via a USB lead or +5v direct to the USB terminals on the board - then everything works fine.If I cannot find out what has blown, I will do a work around by supplying +5v permanently to the USB connections with a separate LM7805.

I had the same issue as you. You wired the end stops incorrectly. you should only use 2 of the three connections on the end stop. if you look carefully you can see on the diagram below that only two of the three wires are used.

dave3d wrote:Using just 2 of the 3 wires, I wired S on ramps to NO on the switch (blue wire) and GND to C (black wire). However disaster. I think I have plugged one of the endstops into the Ramps board upside down. Instead of S to GND this would connect + to GND.

syldcru wrote:You wired the end stops incorrectly. you should only use 2 of the three connections on the end stop. if you look carefully you can see on the diagram below that only two of the three wires are used.

syldcru: You have miss read my post. I did use just 2 of the 3 wires for the limit switch connection as cvoinescu pointed out.

I read that the latest version of Marlin uses normally open contacts which why I wired it that way.It was my fault for plugging it in upside down but nowhere has it been highlighted to use caution and double check the orientation of the plug. It easy to get it wrong.

Built a small circuit board with an LM7805 and superglued it to the RAMPS board. Hey Presto it works!Still not there with my build. Problems now with my extruder.Thanks cvoinescu. I have added you to my Christmas card list.